as in treacherous
formal
causing harm in a way that is gradual or not easily noticed
Most people with this insidious disease have no idea that they are infected. an insidious enemy
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Recent Examples of insidious
As outbreaks become common once again, Americans will have to confront just how insidious and difficult to control this virus can be.
—
Katherine J. Wu, The Atlantic, 18 Dec. 2025
Two decades later, Dholakia feels the situation has turned insidious.
—Viren Naidu, IndieWire, 18 Dec. 2025
Removing the Department of Justice’s regulations prohibiting unfair discriminatory policies takes away critical safeguards against the most insidious forms of exclusion.
—Associate News Editor, MSNBC Newsweek, 10 Dec. 2025
The hysteria about a superior race, the insistence that all would be well if one insidious group was purged—those doctrines had been entirely defeated.
—Joan Silber, New Yorker, 30 Nov. 2025
See All Example Sentences for insidious
Katherine J. Wu, The Atlantic, 18 Dec. 2025
Two decades later, Dholakia feels the situation has turned insidious.
—Viren Naidu, IndieWire, 18 Dec. 2025
Removing the Department of Justice’s regulations prohibiting unfair discriminatory policies takes away critical safeguards against the most insidious forms of exclusion.
—Associate News Editor, MSNBC Newsweek, 10 Dec. 2025
The hysteria about a superior race, the insistence that all would be well if one insidious group was purged—those doctrines had been entirely defeated.
—Joan Silber, New Yorker, 30 Nov. 2025
See All Example Sentences for insidious
Recent Examples of Synonyms for insidious
Adjective
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As challenging and treacherous as international politics could be, Janet didn’t want to return to North Iowa.—
Literary Hub,
Literary Hub,
12 Jan. 2026
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The Traitors season 4 Ready for more shocking betrayals, treacherous twists and cold-blooded murder — but with your favorite reality TV stars and celebrities?—
Rebecca Aizin,
PEOPLE,
9 Jan. 2026
Adjective
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The model predicts target expressions from subtle initial facial changes.—
Jijo Malayil,
Interesting Engineering,
15 Jan. 2026
-
Amazon Essentials Pointed-Toe Flat Want a subtle lift without having to wear heels?—
Nicol Natale,
PEOPLE,
15 Jan. 2026
Adjective
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Plants that provide winter interest, including sedums, goldenrod, blue false indigo, and ornamental grasses.—
Lauren Landers,
Better Homes & Gardens,
11 Jan. 2026
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Today’s teenagers can produce a TikTok video in minutes, but how many of them will learn to analyze the president’s false claim that Tylenol causes autism?—
Mary Ellen Klas,
Twin Cities,
11 Jan. 2026
Adjective
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Gumihos are mythical, fox-like creatures out of Korean folklore known for their nine tails, deceptive behavior, and magical powers.—
Kayti Burt,
Time,
14 Jan. 2026
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There was a bill introduced last legislative session that would have empowered citizens to sue for allegedly deceptive practices, fraud, harassment, intimidation or misrepresentation during the acquisition of land access agreements by carbon pipeline land agents.—
Meghan O’Brien,
States Newsroom,
13 Jan. 2026
Adjective
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Her Ashley is the movie’s fourth and fifth wheel, dismissed as both a perfidious troublemaker and a New Age airhead—a life coach in need of a wife coach.—
Justin Chang,
New Yorker,
22 Aug. 2025
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This perfidious situation, unintentional as its creation may have been, was strongly critiqued as far back as 1983 by Jonathan Crush and Paul Wellings in an article in The Journal of Modern African Studies.—
The Editors,
JSTOR Daily,
15 Aug. 2025
Adjective
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Duplicate collections, wrong dates, incorrect creditor names or accounts listed as unpaid when they were settled are all valid reasons to file a dispute.—
Angelica Leicht,
CBS News,
14 Jan. 2026
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The problem of incorrect citations and false legal statements, which attorneys suspect were written by AI tools, appears to be growing, said Felix De La Torre, general counsel for PERB.—
William Melhado,
Sacbee.com,
13 Jan. 2026
Adjective
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The candidacy challenge contends that Wilcox used the wrong form to file for office in December and left off information that was required.—
Eleanor Dearman,
Fort Worth Star-Telegram,
13 Jan. 2026
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An Amazon driver accompanied by her 16-year-old son came under fire after accidentally stopping at the wrong house in rural North Carolina, according to investigators.—
Mark Price,
Charlotte Observer,
13 Jan. 2026
Cite this Entry
“Insidious.” Merriam-Webster.com Thesaurus, Merriam-Webster, https://www.merriam-webster.com/thesaurus/insidious. Accessed 19 Jan. 2026.
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